The present invention relates generally to digital circuits, and specifically to digital circuits which conserve power in computer memories, particularly in computer devices that run on batteries.
Increasingly, computer devices such as laptops have become portable in response to the demand by consumers to take their work with them for home or for business trips. New devices such as handheld calendars and memo pads have a chief advantage that they too are portable. Such portable computing devices require batteries to run them, and one of the most important problems associated with these computing devices is battery usage. It often takes a long time to recharge a portable computer device, and the user may not be in a situation where he can stop and remain near a particular electrical outlet to run or charge the unit. When the user must become stationary to use the computer device, it defeats the portability feature of the computer. It thus becomes critical to reduce the amount of power usage in portable computer devices so that it is not necessary to recharge these devices so frequently.
Among the many components in a portable computer device is the read only memory (ROM). When a byte or word is received from a memory such as a read only memory (ROM), the state of the byte or word is detected and sent to the computer processor to be acted upon. Meanwhile there is power drawn from the computer device even after the byte or word has been detected, and the state of the byte or word determined. The power that is drawn is referred to as the static current. In such a system, the circuit that detects a series of bits from the ROM is called the ROM bit sensor. Typically, unless there is some method for de-selecting the memory, the bits will continue to drain power from the computer device. De-selecting the memory chip is, however, a comparatively slow process during which static current continues to be drawn.